Metallurgical process



W. E. GREENAWALT. METALLURGICAL PROCESS. APPLICATION FILED use. 21, 1916. RENEWED SEPT. 2, I919.

1,342,804. Patented J 11110 8, 1920.

J a 2 v 24 l9 10 L 2/ 4 I WITNESSES /NVE/VTOR UNITED STATES,

WILLIAM E. GREENAWALT, 0F DENVER, COLORADO.

METALLURGICAL PROCESS.

Specification of Letters Patent.

Patented J une S, 1920.

Application filed December 21, 1916, Serial No. 138,273. Renewed September 2, 1919. Serial No. 321,260.

T 0 all whom it may concern Be it known that I, VVILLIA'M E. GREENA- WALT, a citizen of the United States, residing in the city and county of Denver and State of Colorado, have invented certain new and useful Improvements in Metallurgical Processes, of which the following is a specification.

The invention has for its more immediate object the rendering harmless, or mitigating the evils, in the electrolysis of an impure electrolyte, especially an electrolyte obtained from leaching ores of copper.

This process may be considered a continuation of my pending application Serial No. 15,583, filed March 19, 1915, and, like that application, will be described more particularly to the treatment of copper ores, although it is not intended to limit it to this use alone.

In the electrolysis of impure copper solutions, as for example those obtained from leaching copper ores with an acid sulfate solution, there is always present iron sulfate, which injuriously affects the operation. Ferrous sulfate in the electrolyte is not particularly harmful, but the ferric sulfate is highly detrimental.

If a solution of copper sulfate, containing ferrous sulfate, is electrolyzed, copper is deposited at the cathode while sulfuric acid and ferric sulfate are produced at the anode, as represented by the following equations:

1. CuSO,+H,O:Cu-IH,SO,+O 2. CuSO,-|2FeSO,=Cu-i-Fe (S0 3 The ferric sulfate, finding its way back to the cathode, combines with the deposited copper and is again reduced to the ferrous condition, thus representing a loss of efli-' ciency, as represented by the equation:

3. Cu-l-Fe (S0 =CuSO,+2FeSO,.

4.. Ou, S+Fe (SO,)

CuS|CuSO,+2FeSO 5. cus+Fe, so, =cuso,+2Feso,+s. In the treatment of copper ores by a solvent process there is produced rich and lean copper solutions. The rich copper solutions usually result from the application of the standard solution, while the lean copper solutions usually result from the application. of washwater, or impoverished foul solutions, to wash out the soluble values from the ore, after the rich solutions have been withdrawn.

Usually, if the rich solutions are electrolyzed or not, the lean solutions are chemically precipitated and the precipitate so ob tained plays no further part in the general metallurgical scheme. My present object is to use the precipitate from the lean, or foul, solutions, to reduce, or eliminate, the difliculties in the electrolysis of the rich solutions, and have as an end product for both, the pure electrolytic metal. With this in view a detailed description will be given in connection with the accompanying drawings, although I do not wish to be limited in its application to the preferred method of carrying it out as set forth in the drawings.

In the drawings Figure 1 represents a diagrammatic plan of the process, and Fig. 2, a diagrammatic partial section.

A leaching vat, or other apparatus for dissolving the copper from its ores, is shown at 1. The rich copper solutions flow from the vat through the pipe 2, and the lean solutions through the pipe 22. The rich solution issuing from the vat through the pipe 2, flows into the electrolyzers 3, of which there may be any number. For convenience four are shown. The copper solution as it comes from the ore invariably contains iron salts, so that when the copper solution is electrolyzed in the cells 3, to deposit the copper and regenerate acid, a certain amount offerric sulphate is formed, and when the ferric sulfate accumulates in considerable quantities, the efficiency of the deposition is materially decreased. To overcome this, the rich solution, or electrolyte, is flowed into an agitator 4, where it is agitated with finely divided copper sulfid, whereby, according to equations 4: and 5 the ferric iron is reduced to the ferrous condition while an equivalent of copper goes into solution as the sulfate. The agitation is desired so as to make the reaction quicker and more positive. From the agitator 4, the solution flows into a separator 5, where the copper sulfid is separated from the solution. The clear solution, now having the ferric iron reduced to the ferrous condition, flows into the electroly'zers 6,

where more copper is deposited by the electric current, more acid regenerated, and more ferric iron produced. The copper sulfid from the separator 5, is returned to the agitator to act on fresh solutions, and this is continued until the copper sulfid is exhausted or until it is advisable to otherwise treat it. The separator may be a filter press, or a tank thickener having scrapers in the bottom and arranged so that the thickened copper sulfid at the bottom is lifted through the pump 5" and returned to the agitator while the clear solution overflows on top. Both of these devices are well known standard apparatus and will not need further description. The mechanism 1 in the agitator, rotates rapidly, while that in the thickener, or separator, 5, rotates very slowly. The thickened copper suliid from the separator 5, is elevated through the pipe 5 by means of an air lift 5. From the electrolyzers (3, the electrolyte again flows into an agitator containing copper sulfid 7, similar to l, and then into a separator 8, similar to 5, where the ferric sulfate is again reduced and more. copper from the copper sulfid goes into solution. It then again flows into electrolyzers 9, and this alternate flow from electrolyzers to reducers is continued until the electrolyte is sufficiently impoverished in copper and enriched in acid, and then it is returned to the ore in the vat 1, to dissolve more copper, and go through another cycle. It is returned by means of the pump 17 and the pipe line 10.

The preferred method of obtaining and preparing the copper sulfid will now be described. The lean solutions, as also the excessively foul solutions from which the copper has been largely recovered by electrolysis, are drawn into the precipitating tank 11, where the copper in the solution is preferably precipitated as the sulfid with hydrogen sulfid, produced in the hydrogen sulfid generator 12, from iron suliid and sulfuric acid. The copper sullid sludge is then flowed into the separator 13, where the dilute and regenerated acid solution is separated from the copper sulfid, and may again be used as a lean acid wash. The copper sulfid precipitate, preferably as a thick sludge, is flowed into the agitators 1 and 7, to reduce the ferric salts in the electrolyte, while the copper in the precipitate goes into solution as the sulfate, and is also recovered as electrolytic copper. It has been observed that the cuprous sulfid,Cu S, is a better reducing agent than the cupric sulfid, CuS, and as the precipitate obtained with hydrogen sulfid by reacting with copper sulfate is in the form of cupric sulfid, it is desirable to convert as much as possible of the cupric sulfid into the cuprous sulfid, and

it is also advisable at the same time to convert some of the precipitated copper sulfid into the oxid. At quite a low heat, about 115 deg. (1., some of the sulfur of the cupric sulfid is given off, and the oxidation to cuprous sulfid and oxid begins. The relative amounts of the cuprous sulfid and oxid will depend largely on the nature of the atmosphere in the furnacewhether it is somewhat reducing or highly oxidizing. If it is desired to treat the copper sulfid precipitate to make it more effective in the process, the thickened sludge from the separator 13, is passed into a filter 18, where as much as possible of the moisture is removed. It is then introduced into a furnace 20, where as much as desired of the sulfur is driven off. The precipitate thus treated is then introduced into the agitators 4; and 5. If desired some of this roasted precipitate may be applied to the rich so lution issuing from the vat, in the tank 23, before it passes to the electrolyzers. In this way some of the iron may be precipitated from the neutral solution before it passes to the electrolyzers, and thus make easier the reduction of the remaining iron. It would be quite feasible to obtain cuprous sulfid precipitate by the process set forth in my Patent No. 1,180,844, April 25, 1916, by precipitating from chlorid solution; in this case, however, care would have to be taken to wash the sulfid precipitate free from chlorids, as the chlorids would affect the electrolyte injuriously.

If the precipitate is roasted and much of the copper converted into the oxid, and the roasted precipitate applied to practically the neutral rich copper solution in tank 23, and then agitated, especially with air, much of the iron will be precipitated out of the copper solution, although it appears to be quite difficult to get a total elimination of the iron. Such an elimination, however, with a practically pure copper compound, free from iron, as the precipitate necessarily is, greatly helps to mitigate the evil of the ferric salts, and makes it easier to maintain the remaining iron in the electrolyte in a reduced condition, so that its deleterious action is not serious or fatal to successful operation.

In operating the process the most satisfactory results will usually be obtained by roasting a portion of the precipitate from the lean, or foul, solution, to practically regenerated, solution, with practically its full strength of regenerated acid, is returned to the ore to dissolve more copper from the ore. Ample time should be given for the reaction, and a large volume of solution and copper sulfid should be continuously under the reducing treatment.

I claim:

1. A metallurgical process which consists in agitating an electrolyte containing ferric iron with a sulfid reducing agent practically free from iron, continuously withdrawing a portion of the mixture of sulfid and electrolyte and separating the sulfid from the electrolyte, and returning the reduced electrolyte to the electrolyzer and the copper sulfid to the agitator.

2. A metallurgical process which consists in treating ores of metals with an acid solution to dissolve the metals, electrolyzing the rich metal solution containing salts of the variable valent elements to deposit the metals and regenerate acid whereby the valency of the variable valent elements is raised, precipitating the metals in the lean solution as sulfids, agitating the precipitate with the electrolyte, withdrawing a portion of the mixture of precipitate and electrolyte from the agitator, separating the precipitate from the reduced electrolyte, returning the reduced electrolyte to the electrolyzer and the precipitate to the agitator, and continuing this until the electrolyte is sufliciently impoverished in metals and enriched in acid, and then returning it to the ore to dissolve more metals.

3. A metallurgical process which consists in continuously agitating a stream of electrolyte containing ferric iron with a sulfid reducing agent practically free from iron, withdrawing the electrolyte and reducing agent from the agitator in a continuous stream, and continuously separating the electrolyte and reducing agent, and continuously returning the electrolyte to the electrolyzer and the sulfid reducing agent to the agitator.

4. A metallurgical process which consists in electrolyzing a copper solution containing salts of the variable elements, chemically precipitating copper from its solution as sulfid, reducing the sulfur content of the precipitated copper sulfid, and treating the electrolyte therewith.

WILLIAM E. GREENAWALT.

Witnesses:

H. GRAQE SNYDER, CoRA M. GREENAWALT. 

